Unmanned aircraft, information processing method, and recording medium

ABSTRACT

An unmanned aircraft includes: a sensor that includes at least a microphone that generates sound data; and a processor. The processor determines quality of a target sound using the sound data generated by the microphone, obtains a positional relationship between the unmanned aircraft and a sound source of the target sound using data generated by the sensor, and controls movement of the unmanned aircraft to control a distance between the unmanned aircraft and the sound source of the target sound, in accordance with the quality of the target sound and the positional relationship.

CROSS REFERENCE TO RELATED APPLICATION(S)

This is a continuation application of PCT International Application No.PCT/JP2019/043783 filed on Nov. 8, 2019, designating the United Statesof America, which is based on and claims priority of Japanese PatentApplication No. 2019-027725 filed on Feb. 19, 2019. The entiredisclosures of the above-identified applications, including thespecifications, drawings and claims are incorporated herein by referencein their entirety.

FIELD

The present disclosure relates to an unmanned aircraft, an informationprocessing method, and a recording medium.

BACKGROUND

Patent Literature (PTL) 1 discloses an unmanned airplane that performs aprocess for removing background noise from audio data collected by abackground microphone.

CITATION LIST Patent Literature

PTL 1: Japanese Unexamined Patent Application Publication (Translationof PCT Application) No. 2017-502568

SUMMARY Technical Problem

Unfortunately, the technology disclosed in PTL 1 is developed withlittle regard for safety of a sound source. Thus, it may be difficult toenhance quality of sound recording in addition to ensuring the safety.

In view of this, the present disclosure provides an unmanned aircraft,an information processing method, and a recording medium that arecapable of enhancing quality of sound recording in addition to ensuringsafety of a sound source.

Solution to Problem

An unmanned aircraft according to the present disclosure includes: asensor that includes at least a microphone that generates sound data;and a processor, wherein the processor determines quality of a targetsound using the sound data generated by the microphone, obtains apositional relationship between the unmanned aircraft and a sound sourceof the target sound using data generated by the sensor, and controlsmovement of the unmanned aircraft to control a distance between theunmanned aircraft and the sound source of the target sound, inaccordance with the quality of the target sound and the positionalrelationship.

It should be noted that general or specific aspects of the presentdisclosure may be implemented to a system, a method, an integratedcircuit, a computer program, a computer-readable recording medium suchas a Compact Disc-Read Only Memory (CD-ROM), or any given combinationthereof.

Advantageous Effects

The unmanned aircraft, the information processing method, and therecording medium according to the present disclosure are capable ofenhancing the quality of sound recording in addition to ensuring thesafety of the sound source.

BRIEF DESCRIPTION OF DRAWINGS

These and other advantages and features will become apparent from thefollowing description thereof taken in conjunction with the accompanyingDrawings, by way of non-limiting examples of embodiments disclosedherein.

FIG. 1 illustrates an external view of an unmanned aircraft and acontroller according to an embodiment.

FIG. 2 is a plan view of the unmanned aircraft seen from above,according to the embodiment.

FIG. 3 is a cross-sectional view of the unmanned aircraft along lineIII-III illustrated in FIG. 2.

FIG. 4 is a block diagram illustrating a configuration of the unmannedaircraft according to the embodiment.

FIG. 5 is a flowchart illustrating an example of an operation performedfor sound recording control of the unmanned aircraft according to theembodiment.

FIG. 6 is a flowchart illustrating an example of a process performed bythe unmanned aircraft to determine quality of a target sound.

FIG. 7 illustrates an example of a method of calculating asignal-to-noise (S/N) ratio as an indicator of the quality of the targetsound.

FIG. 8A illustrates a first situation as an example of the operationperformed for sound recording control of the unmanned aircraft accordingto the embodiment.

FIG. 8B illustrates a second situation as an example of the operationperformed for sound recording control of the unmanned aircraft accordingto the embodiment.

FIG. 8C illustrates a third situation as an example of the operationperformed for sound recording control of the unmanned aircraft accordingto the embodiment.

FIG. 9A illustrates a fourth situation as an example of the operationperformed for sound recording control of the unmanned aircraft accordingto the embodiment.

FIG. 9B illustrates a fifth situation as an example of the operationperformed for sound recording control of the unmanned aircraft accordingto the embodiment.

FIG. 9C illustrates a sixth situation as an example of the operationperformed for sound recording control of the unmanned aircraft accordingto the embodiment.

FIG. 10A illustrates a seventh situation as an example of the operationperformed for sound recording control of the unmanned aircraft accordingto the embodiment.

FIG. 10B illustrates an eighth situation as an example of the operationperformed for sound recording control of the unmanned aircraft accordingto the embodiment.

FIG. 10C illustrates a ninth situation as an example of the operationperformed for sound recording control of the unmanned aircraft accordingto the embodiment.

FIG. 11A illustrates a tenth situation as an example of the operationperformed for sound recording control of the unmanned aircraft accordingto the embodiment.

FIG. 11B illustrates an eleventh situation as an example of theoperation performed for sound recording control of the unmanned aircraftaccording to the embodiment.

FIG. 12A illustrates a twelfth situation as an example of the operationperformed for sound recording control of the unmanned aircraft accordingto the embodiment.

FIG. 12B illustrates a thirteenth situation as an example of theoperation performed for sound recording control of the unmanned aircraftaccording to the embodiment.

FIG. 13 is a table illustrating an example of a relationship between areference S/N ratio and a purpose.

FIG. 14 is a flowchart illustrating an example of the operation forsound recording control of the unmanned aircraft according to avariation.

FIG. 15 is a flowchart illustrating another example of the operation forsound recording control of the unmanned aircraft according to avariation.

DESCRIPTION OF EMBODIMENT (Underlying Knowledge Forming Basis of thePresent Disclosure)

As described above, the unmanned airplane disclosed in PTL 1 performsthe process for removing the background noise, which is caused from apropellant unit like a rotor included in the unmanned airplane, from thecollected audio data. However, this unmanned airplane does not use arelative positional relationship with the sound source that is a targetfor collecting the audio data. For this reason, the sound source may notbe present in a sound recording area of a sound-source collectingmicrophone included in the unmanned airplane to detect a target soundfrom the sound source. In this sound recording area, the sound-sourcecollecting microphone effectively performs sound recording. When thesound source is not present in the sound recording area of thesound-source collecting microphone, the sound-source collectingmicrophone is unable to effectively pick up the target sound. As aresult, the background noise is relatively more collected. Thisincreases noise components of the audio data obtained by thesound-source collecting microphone and thus reduces a signal-to-noise(S/N) ratio. Thus, even if the process for removing the background noisefrom the obtained audio data is performed, it is difficult to obtainaudio data of high quality.

To address this, the unmanned airplane may approach the sound source tocollect the audio data so that the target sound from the sound source isrelatively more collected than the background noise. The unmannedairplane may move in a direction to approach the sound source andcollect the audio data at a close distance from the sound source. Inthis case, if the unmanned airplane is out of control or has a problemwith an actuator that develops a thrust force of the unmanned airplane,the unmanned airplane may fall down onto the sound source. On thisaccount, safety of the sound source is to be ensured by taking safetymeasures, such as enclosing the sound source with a guard net. Morespecifically, ensuring the safety of the sound source is difficultwithout additionally expending energy and cost of manufacturing andplacing the guard net.

In order to solve the above problem, an unmanned aircraft according tothe present disclosure includes: a sensor that includes at least amicrophone that generates sound data; and a processor, wherein theprocessor determines quality of a target sound using the sound datagenerated by the microphone, obtains a positional relationship betweenthe unmanned aircraft and a sound source of the target sound using datagenerated by the sensor, and controls movement of the unmanned aircraftto control a distance between the unmanned aircraft and the sound sourceof the target sound, in accordance with the quality of the target soundand the positional relationship.

Thus, the quality of the target sound can be ensured while the distancebetween the unmanned aircraft and the sound source is controlled. Thisenhances the quality of sound recording in addition to ensuring safetyof the sound source.

It is possible that when the quality of the target sound is higher thana predetermined goal quality, the processor causes the unmanned aircraftto move away from the sound source.

Thus, the unmanned aircraft moves away from the sound source within thearea to maintain the goal quality. This further enhances the safety ofthe sound source.

It is possible that when causing the unmanned aircraft to move away fromthe sound source, the processor causes the unmanned aircraft to move toany position between a current position of the unmanned aircraft and aposition at which the quality of the target sound reaches thepredetermined goal quality.

This enhances the safety of the sound source while ensuring the qualityof sound recording without fall below the goal quality.

It is possible that when the quality of the target sound is lower thanthe predetermined goal quality, the processor causes the unmannedaircraft to approach the sound source.

Thus, the unmanned aircraft approaches the sound source within the areato satisfy the goal quality. This further enhances the quality of soundrecording in addition to ensuring the safety of the sound source.

It is possible that the processor further obtains distance informationindicating a predetermined distance from the sound source, and whencausing the unmanned aircraft to approach the sound source, theprocessor controls the movement of the unmanned aircraft in accordancewith the distance information and the positional relationship to causethe unmanned aircraft not to approach any closer to the sound sourcethan a position at the predetermined distance from the sound source.

Thus, the unmanned aircraft is caused to move in the direction toapproach the sound source within the area to ensure the safety of thesound source. As a result, at least the predetermined distance is leftbetween the sound source and the unmanned aircraft. This reliablyensures the safety of the sound source in addition to enhancing thequality of sound recording.

It is possible that the unmanned aircraft further includes: an actuatorthat changes at least one of an orientation of the microphone or anamount of outward projection of the microphone from the unmannedaircraft, wherein when the quality of the target sound is lower than thepredetermined goal quality even after the processor controls themovement of the unmanned aircraft in accordance with the distanceinformation and the positional relationship to cause the unmannedaircraft to move, to approach the sound source, to the position at thepredetermined distance from the sound source, the processor causes theactuator to change at least one of the orientation of the microphone orthe amount of outward projection of the microphone from the unmannedaircraft.

Thus, when causing the orientation of the microphone to be changed bycontrolling the actuator, the processor can orient a direction in whichthe microphone has a high sensitivity toward the sound source. As aresult, the high-sensitivity direction of the microphone is aligned withthe direction of the sound source. Thus, the sound pressure level of thetarget sound with respect to the sound pressure level of the noise canbe relatively increased, which enhances the quality of sound recording.

When causing the amount of outward projection of the microphone from theunmanned aircraft to be changed by controlling the actuator, theprocessor allows the microphone to project outwardly from the unmannedaircraft to approach the sound source. As a result, the microphone isdistanced from the unmanned aircraft that is a noise source, and thusthe sound pressure level of the noise can be reduced. Moreover, themicrophone approaches the sound source in this case. Thus, the soundpressure level of the target sound with respect to the sound pressurelevel of the noise can be relatively increased. This effectivelyenhances the quality of sound recording.

It is possible that the processor calculates a signal-to-noise (S/N)ratio using the target sound and noise related to flight of the unmannedaircraft, as an indicator for determining the quality.

This allows the quality of the target sound to be easily determined.

It is possible that the processor further obtains a goal S/N ratioprecalculated using the noise related to the flight of the unmannedaircraft, as the predetermined goal quality, and determines the qualityof the target sound by comparing the goal S/N ratio obtained and the S/Nratio calculated.

The prior calculation of the goal S/N ratio can reduce an amount ofprocessing load of determining the quality of sound recording.

The processor may control the unmanned aircraft so that the unmannedaircraft moves in the horizontal direction. As a result, the unmannedaircraft moves in the horizontal direction away from the sound source.This leaves a distance from the sound source in the horizontaldirection. In this case, the unmanned aircraft does not move to aposition higher than the current position. Thus, an impact in case offalling of the unmanned aircraft can be reduced to ensure the safety ofthe sound source.

It is possible that the processor causes the unmanned aircraft toapproach ground.

As a result, the unmanned aircraft moves in the direction to approachthe ground to approach the sound source. This allows the unmannedaircraft to approach the sound source while maintaining the distancefrom the sound source in the horizontal direction. In this way, unmannedaircraft 100 is closer to the ground than the current position is. Thus,an impact in case of falling of the unmanned aircraft can be reduced toensure the safety of the sound source.

The processor may obtain the positional relationship using the sounddata. In this case, the mounted microphone alone allows the quality ofsound recording to be enhanced in addition to ensuring the safety of thesound source. This eventually suppresses an increase in gross weight ofthe unmanned aircraft.

It is possible that the sensor further includes an image sensor thatgenerates image data, and the processor obtains the positionalrelationship using the image data generated by the image sensor.

In this way, the processor obtains the positional relationship using theimage data. Thus, the positional relationship with high precision can beobtained.

It is possible that the sensor further includes a ranging sensor thatgenerates ranging data, and the processor obtains the positionalrelationship using the ranging data generated by the ranging sensor.

In this way, the processor obtains the positional relationship using theranging data. Thus, the positional relationship with high precision canbe obtained.

It is possible that the processor determines a goal distance inaccordance with the quality of the target sound, the positionalrelationship, and the predetermined goal quality, and controls themovement of the unmanned aircraft to cause the distance between theunmanned aircraft and the sound source to reach the goal distance.

As a result, the unmanned aircraft can move to the positioncorresponding to the predetermined goal quality.

It is possible that the positional relationship is at least one of (i)the distance between the unmanned aircraft and the sound source, (ii) aposition of the sound source with respect to the unmanned aircraft, or(iii) a direction from the unmanned aircraft to the sound source.

It should be noted that general or specific aspects of the presentdisclosure may be implemented to a system, a method, an integratedcircuit, a computer program, a computer-readable recording medium suchas a Compact Disc-Read Only Memory (CD-ROM), or any given combinationthereof.

Hereinafter, the unmanned aircraft according to an aspect of the presentdisclosure will be described in detail with reference to the drawings.

The following embodiments are specific examples of the presentdisclosure. The numerical values, shapes, materials, elements,arrangement and connection configuration of the elements, steps, theorder of the steps, etc., described in the following embodiments aremerely examples, and are not intended to limit the present disclosure.Among elements in the following embodiments, those not described in anyone of the independent claims indicating the broadest concept of thepresent disclosure are described as optional elements.

EMBODIMENT

The following describes an embodiment with reference to FIG. 1 to FIG.12B.

[1. Configuration]

FIG. 1 illustrates an external view of an unmanned aircraft and acontroller according to the embodiment. FIG. 2 is a plan view of theunmanned aircraft seen from above according to the embodiment.

As illustrated in FIG. 1, unmanned aircraft 100 receives, fromcontroller 200, an operation signal based on an operation performed oncontroller 200 by a user. Unmanned aircraft 100 flies according to thereceived operation signal. During flight, unmanned aircraft 100 maycapture an image using camera 107 included in unmanned aircraft 100,according to the received operation signal. Image data captured bycamera 107 may be transmitted to mobile terminal 300 described later.

Receiving the operation from the user, controller 200 transmits theoperation signal based on the received operation to unmanned aircraft100. Controller 200 may hold mobile terminal 300 having a display, suchas a smartphone.

Mobile terminal 300 receives the image data captured by camera 107 ofunmanned aircraft 100, and displays the image data received in realtime, for example.

Thus, while visually verifying in real time the image data captured bycamera 107 of unmanned aircraft 100 and displayed on mobile terminal300, the user can operate controller 200 to change a flight state, whichis at least one of position or attitude of unmanned aircraft 100 duringflight. This allows the user to freely change an imaging area of camera107 of unmanned aircraft 100.

Unmanned aircraft 100 includes four generators 110, four ducts 130, mainbody 140, and four arms 141.

Each of generators 110 generates a force to fly unmanned aircraft 100.To be more specific, each of generators 110 produces an airflow togenerate the force to fly unmanned aircraft 100. Each of generators 110includes: rotor 111 that rotates to generate an airflow; and actuator112 that rotates rotator 111. Rotor 111 and actuator 112 have rotationaxes roughly parallel to each other in a vertical direction whenunmanned aircraft 100 is placed on a horizontal plane, and generate anairflow flowing downward from above. Thus, four generators 110 generatea thrust force for unmanned aircraft 100 to ascend and also generate aforce for unmanned aircraft 100 to fly. Actuator 112 is a motor, forexample.

When viewed from above, four generators 110 are arranged at angularintervals of 90 degrees around main body 140. To be more specific, fourgenerators 110 are arranged circularly to encompass main body 140.

Rotor 111 provided for each of generators 110 includes one propeller asillustrated. However, this is not intended to be limiting. Rotor 111 mayinclude two contra-rotating propellers that rotate about the samerotation axis in opposite directions.

FIG. 3 is a cross-sectional view of the unmanned aircraft along lineIII-III illustrated in FIG. 2. More specifically, FIG. 3 is across-sectional view of generator 110 and duct 130, which is disposedcorresponding to this generator 110, along a plane passing through therotation axis of rotor 111.

Each of ducts 130 is provided for a corresponding one of four generators110. Each of ducts 130 is disposed to cover the corresponding one ofgenerators 110 laterally, or more specifically, disposed to cover thisgenerator 110 in a direction roughly orthogonal to the rotational axisof rotor 111 of this generator 110. For example, each of four ducts 130covers the corresponding one of generators 140 laterally over a lengthof this generator 110 in a rotational axis direction. To be morespecific, each of four ducts 130 includes space 131 in which generator110 is disposed and which is a circular cylinder passing through thisduct 130 in a vertical direction. Each of ducts 130 has a shape thatdecreases in thickness in a downstream direction in which the airflowgenerated by the corresponding one of generators 110 flows. Morespecifically, each of four ducts 130 has an outer surface thatapproaches an inner surface of this duct 130 in the downstream directionin which the airflow generated by the corresponding one of generators110 flows. In other words, each of four ducts 130 has a shape thattapers down toward the downstream of the airflow generated by thecorresponding one of generators 110. An end part of the inner surface ofduct 130 on an upstream side of the airflow is rounded. To be morespecific, duct 130 has this end part that decreases in inside diameterof duct 130 in the direction in which the airflow flows. This allows airto easily enter duct 130 and thus enhances flight performance. Moreover,this achieves weight reduction of duct 130, and weight reduction ofunmanned aircraft 100 eventually. Here, the end part may have a linearshape along the direction in which the airflow flows.

Main body 140 is a cylindrical box-like component for example, or morespecifically, a housing. Main body 140 contains electronic devicesincluding a processor, a memory, a battery, and various sensors. Theshape of main body 140 is not limited to a cylinder, and may be abox-like shape in a different form, such as a quadrangular prism.Moreover, four microphones 105, gimbal 106, and camera 107 are disposedoutside main body 140. For example, each of four microphones 105 isdisposed in a region, on a side surface of main body 140, between tworegions among four regions in each of which one of four arms 141corresponding to four generators 110 is connected. More specifically,with main body 140 being the center, each of microphones 105 is disposedto face in a direction shifted by 45 degrees with respect to a directionin which generator 110 is located.

Each of four arms 141 is a component that connects main body 140 to acorresponding one of four ducts 130. Each of four arms 141 has one endfixed to main body 140 and the other end fixed to the corresponding oneof four ducts 130.

FIG. 4 is a block diagram illustrating a configuration of the unmannedaircraft according to the embodiment. More specifically, FIG. 4 is ablock diagram illustrating a function of processor 101 implemented by ahardware configuration of unmanned aircraft 100.

As illustrated in FIG. 4, unmanned aircraft 100 includes processor 101,global positioning system (GPS) receiver 102, acceleration sensor 103,gyroscope sensor 104, four microphones 105, gimbal 106, camera 107,ranging sensor 108, communication interface (IF) 109, and fourgenerators 110.

Processor 101 obtains detection results from various sensors includingacceleration sensor 103, gyroscope sensor 104, four microphones 105, animage sensor of camera 107, and ranging sensor 108 and also obtains areception result from GPS receiver 102 or communication IF 109, forexample. In response to the obtained detection results or receptionresult, processor 101 performs a corresponding process by executing apredetermined program stored in a memory or storage that is not shown.In this case, processor 101 controls at least one of gimbal 106, camera107, and four generators 110.

GPS receiver 102 receives information indicating a position of this GPSreceiver 102 from an artificial satellite that includes a GPS satellite.To be more specific, GPS receiver 102 detects a current position ofunmanned aircraft 100. GPS receiver 102 sequentially outputs thedetected current position of unmanned aircraft 100 to processor 101 or astorage that is not shown.

Acceleration sensor 103 detects an acceleration of unmanned aircraft 100for each of three different directions.

Gyroscope sensor 104 detects an angular speed for each rotation aboutthree axes along the three different directions of unmanned aircraft100.

Each of microphones 105 is directional and has a property of being ableto pick up higher-quality sound within a sound pickup area having apredetermined angular range with respect to a specific direction thanwithin an angular range outside the sound pickup area.

Each of microphones 105 is an example of a sensor. The predeterminedangular range is 90 degrees or less for example, and is athree-dimensional angular range extending from a position of directionalmicrophone 105. Each of microphones 105 may be a microphone arrayincluding a plurality of microphone elements. Each of microphones 105picks up sound to sequentially generate sound data and then sequentiallyoutputs the generated sound data to processor 101 or a storage that isnot shown. When receiving the sound data, the storage sequentiallystores the sound data received. Here, the storage may store the sounddata in association with time information indicating a current time ofday, for example.

Gimbal 106 is a device that keeps a triaxial attitude of camera 107constant. More specifically, even if the attitude of unmanned aircraft100 changes, gimbal 106 maintains a desirable attitude of camera 107with respect to, for example, a terrestrial coordinate system. Here, thedesirable attitude may be defined by an imaging direction of camera 107that is included in the operation signal received from controller 200.

Camera 107 is a device that includes an optical system, such as a lens,and the image sensor. Camera 107 is an example of the sensor. Camera 107captures an image to sequentially generate image data and sequentiallyoutputs the generated image data to processor 101 or a storage. Whenreceiving the image data, the storage sequentially stores the image datareceived. Here, the storage may store the image data in association withtime information indicating a current time of day, for example.

Ranging sensor 108 detects a distance between ranging sensor 108 and anear subject. For example, ranging sensor 108 is an ultrasonic sensor, atime-of-flight (TOF) camera, or a light detection and ranging (LIDAR)sensor. Ranging data generated by ranging sensor 108 may be data inwhich a direction with respect to ranging sensor 108 is associated witha distance measured to the near subject in this direction. Rangingsensor 108 is fixed at a predetermined position of unmanned aircraft100. On this account, a positional relationship between thispredetermined position and a reference position of unmanned aircraft100, such as the center of main body 140 of unmanned aircraft 100, isfixed. Thus, a detection result given by ranging sensor 108 allowsunmanned aircraft 100 to calculate a positional relationship between thereference position of unmanned aircraft 100 and the near subject.Ranging sensor 108 is an example of the sensor. Ranging sensor 108performs distance measurement to sequentially generate ranging data, andsequentially outputs the generated ranging data to processor 101 or astorage. When receiving the ranging data, the storage sequentiallystores the received ranging data. Here, the storage may sequentiallystore the ranging data in association with time information indicating acurrent time of day, for example. Note that unmanned aircraft 100 mayinclude a plurality of ranging sensors 108 located on different placesof unmanned aircraft 100. The plurality of ranging sensors 108 arecapable of detecting distances from unmanned aircraft 100 to subjectspresent in different directions.

Communication IF 109 is a communication interface that communicates withcontroller 200 or mobile terminal 300. Communication IF 109 includes acommunication interface for receiving a transmission signal fromcontroller 200, for example. Communication IF 109 may be a communicationinterface to wirelessly communicate with mobile terminal 300, or morespecifically, may be a wireless local area network (LAN) interface thatmeets IEEE 802.11a, 11b, 11g, 11n, 11ac, and 11ax standards, forexample.

Four generators 110 are described above, and thus detailed descriptionis omitted here.

Processor 101 includes functional components including sound pickupprocessor 101 a, quality determiner 101 b, sound source determiner 101c, position detector 101 d, flight controller 101 e, video controller101 f, and obstruction detector 101 g. Note that each of processors 101a to 101 g sequentially performs a corresponding process using detectiondata sequentially detected by the various sensors and a result of theprocess sequentially performed by a corresponding processor. Then, theprocessor sequentially outputs the obtained process result to apredetermined destination.

Sound pickup processor 101 a obtains four pieces of sound data generatedthrough sound pickup by four microphones 105, and performs predeterminedsound processing on each of the obtained four pieces of sound data.Sound pickup processor 101 a includes noise processor 101 aa and noiselevel calculator 101 ab. Noise processor 101 aa performs a sound sourceseparation process to separate the obtained sound data into a targetsound and a noise, which is related to flight of unmanned aircraft 100.The noise associated with unmanned aircraft 100 (hereinafter, simplyreferred to as the noise) refers to a noise caused when generator 110 ofunmanned aircraft 100 is actuated, for example. Noise processor 101 aaextracts the noise or the target sound by applying a directional filter,which is used for obtaining directivity in any direction, to an audiosignal obtained from each of the plurality of microphone elementsincluded in each of microphones 105. As a result, the noise is separatedfrom the target sound. Following this, noise level calculator 101 abcalculates a sound pressure level of the noise separated by noiseprocessor 101 aa and a sound pressure level of the target soundseparated by noise processor 101 aa. As a result, sound pickup processor101 a extracts the noise and the target sound for each of the fourpieces of sound data generated through sound pickup by four microphones105. Note that noise level calculator 101 ab may reduce noise includedin the sound data by performing predetermined sound processing throughfiltering a sound component in a predetermined frequency band. The soundcomponent in the predetermined frequency band is in a frequency band ofnoise caused by rotation of rotor 111 of generator 110, for example.

Quality determiner 101 b determines whether quality of the target soundis higher or lower than a predetermined goal quality, using the soundpressure level of the noise and the sound pressure level of the targetsound obtained by sound pickup processor 101 a. More specifically,quality determiner 101 b calculates an S/N ratio of the target sound tothe noise as an indicator for determining the quality of the targetsound, using the sound pressure level of the noise and the soundpressure level of the target sound. Quality determiner 101 b obtains agoal S/N ratio that is calculated using the S/N ratio calculated usingthe target sound and the noise, as a predetermined goal quality. Then,quality determiner 101 b determines the quality of the target sound bycomparing the obtained goal S/N ratio and the calculated S/N ratio.Here, the goal S/N ratio may be in a range of S/N ratio with respect toa reference S/N ratio. For example, the goal S/N ratio may be within arange of plus or minus 1 with respect to the reference S/N ratio. Notethat the goal S/N ratio may be previously stored in a memory or storagethat is not shown, or in an external device. To be more specific,quality determiner 101 b may obtain the goal S/N ratio by reading fromthe memory or storage that is not shown, or from the external device viacommunication IF 109.

Quality determiner 101 b determines whether the S/N ratio is higher orlower than the goal S/N ratio. If the S/N ratio is higher than the goalS/N ratio, or more specifically, if the S/N ratio is higher than anupper limit of the range of the goal S/N ratio, quality determiner 101 bdetermines that the quality is high. If the S/N ratio is lower than thegoal S/N ratio, or more specifically, if the S/N ratio is lower than alower limit of the range of the goal S/N ratio, quality determiner 101 bdetermines that the quality is low. Quality determiner 101 b maydetermine the quality of the target sound for the sound data having thehighest sound pressure level obtained by sound pickup processor 101 a,among the four pieces of sound data obtained from four microphones 105.Thus, quality determiner 101 b may not determine the quality of thetarget sounds for the other pieces of sound data.

Sound source determiner 101 c obtains a positional relationship betweenunmanned aircraft 100 and a sound source of the target sound(hereinafter, simply referred to as the “sound source”), using at leastone of: the sound data outputted from four microphones 105; the imagedata outputted from camera 107; or the ranging data outputted fromranging sensor 108. Sound source determiner 101 c outputs the obtainedpositional relationship to flight controller 101 e.

Suppose that the positional relationship is obtained using the sounddata generated by four microphones 105. In this case, sound sourcedeterminer 101 c uses the sound data to determine, as the positionalrelationship, at least one of (i) a sound source direction of a soundsource with respect to unmanned aircraft 100; (ii) a position of thesound source with respect to unmanned aircraft 100; or (iii) a distanceto the sound source with respect to unmanned aircraft 100. The soundsource direction of the sound source with respect to unmanned aircraft100 refers to a direction from unmanned aircraft 100 toward the soundsource. The position of the sound source with respect to unmannedaircraft 100 refers to a relative position of the sound source withrespect to unmanned aircraft 100. The distance to the sound source withrespect to unmanned aircraft 100 refers to a distance measured fromunmanned aircraft 100 to the sound source. In this way, sound sourcedeterminer 101 c obtains each of these determination results as thepositional relationship between unmanned aircraft 100 and the soundsource.

For example, sound source determiner 101 c may compare the four piecesof sound data obtained from four microphones 105 and determine, as beingthe sound source direction, a direction in which the sound pressure ofthe target sound is estimated to be greater. Sound source determiner 101c may compare a plurality of pieces of data that are obtained from theplurality of microphone elements of microphone 105 and included in eachof the four pieces of sound data obtained from four microphones 105.Then, sound source determiner 101 c may determine, as being the soundsource direction, a direction in which the sound pressure of the targetsound is estimated to be greater. Moreover, sound source determiner 101c may obtain loudness of the target sound emitted from the sound source.Then, sound source determiner 101 c may estimate a distance to the soundsource by comparing the obtained loudness of the target sound with thesound pressures of the target sound included in the sound data generatedby four microphones 105. In this case, the loudness of the target soundfrom the sound source may be predetermined for estimation of thedistance to the sound source. Furthermore, sound source determiner 101 cmay estimate the relative position of the sound source with respect tounmanned aircraft 100, using the determined sound source direction andthe distance to the sound source.

Suppose that the positional relationship is obtained using the imagedata generated by the image sensor of camera 107. In this case, soundsource determiner 101 c uses the image data to determine at least one of(i) the sound source direction of the sound source with respect tounmanned aircraft 100; (ii) the position of the sound source withrespect to unmanned aircraft 100; or (iii) the distance to the soundsource with respect to unmanned aircraft 100. In this way, sound sourcedeterminer 101 c obtains each of these determination results as thepositional relationship between unmanned aircraft 100 and the soundsource. For example, sound source determiner 101 c may determine atleast one of the position of the sound source, the distance to the soundsource, or the sound source direction, by recognizing a color, shape, ortype of the sound source that is predetermined through image processingperformed on the image data.

Suppose that the positional relationship is obtained using the rangingdata generated by ranging sensor 108. In this case, sound sourcedeterminer 101 c uses the ranging data to determine at least one of (i)the sound source direction of the sound source with respect to unmannedaircraft 100; (ii) the position of the sound source with respect tounmanned aircraft 100; or (iii) the distance to the sound source withrespect to unmanned aircraft 100. In this way, sound source determiner101 c obtains each of these determination results as the positionalrelationship between unmanned aircraft 100 and the sound source. Forexample, sound source determiner 101 c may construct a three-dimensionalmodel using the ranging data. Then, sound source determiner 101 c maydetermine at least one of the position of the sound source, the distanceto the sound source, or the sound source direction, by recognizing athree-dimensional geometry of the sound source from the constructedthree-dimensional model.

Suppose that the sound source direction is determined using the sounddata or the image data. In this case, sound source determiner 101 c mayobtain a distance to a subject present in the sound source directiondetermined from the ranging data, and then estimate the relativeposition of the sound source with respect to unmanned aircraft 100. Inthis way, sound source determiner 101 c may determine a relativepositional relationship between unmanned aircraft 100 and the soundsource, by determining the sound source direction and the distance fromunmanned aircraft 100 to the sound source using the data generated bythe sensors.

Moreover, sound source determiner 101 c may obtain position informationof the sound source from the sound source. Then, sound source determiner101 c may use this information to determine the sound source directionwith respect to unmanned aircraft 100 or the relative position of thesound source with respect to unmanned aircraft 100.

The sound source may be a person, a speaker, or a vehicle, for example.

Position detector 101 d obtains a detection result given by GPS receiver102 and detects a current position of unmanned aircraft 100.

Flight controller 101 e controls a flight state of unmanned aircraft 100by controlling the number of revolutions of actuator 112 of generator110, in accordance with the current position of unmanned aircraft 100detected by position detector 101 d, a flight speed and a flightattitude of unmanned aircraft 100 obtained from the detection resultsgiven by acceleration sensor 103 and gyroscope sensor 104, and theoperation signal received from controller 200 via communication IF 109.More specifically, flight controller 101 e performs normal control tocontrol the flight state of unmanned aircraft 100 according to anoperation performed on controller 200 by the user.

Moreover, flight controller 101 e performs sound recording controlseparately from the normal control. In the sound recording control,flight controller 101 e controls movement of unmanned aircraft 100 tocontrol a distance between unmanned aircraft 100 and the sound source,in accordance with the quality of the target sound determined by qualitydeterminer 101 b and the positional relationship between unmannedaircraft 100 and the sound source determined by sound source determiner101 c.

If quality determiner 101 b determines that the quality of the targetsound is lower than the goal quality, flight controller 101 e controlsthe movement of unmanned aircraft 100 for flight-state control in thesound recording control so that unmanned aircraft 100 moves away fromthe sound source, for example. As a result, unmanned aircraft 100 fliesin a direction away from the sound source.

When controlling the movement of unmanned aircraft 100 so that unmannedaircraft 100 moves away from the sound source, flight controller 101 eperforms control to move unmanned aircraft 100 to any position betweenthe current position of unmanned aircraft 100 detected by positiondetector 101 d and a position at which the quality of the target soundreaches the goal quality. In this case, flight controller 101 e maydetermine, as a goal distance, a distance between the sound source andthe position at which the quality of the target sound reaches the goalquality, for example. Then, flight controller 101 e may control themovement of unmanned aircraft 100 so that the distance between unmannedaircraft 100 and the sound source reaches the goal distance.

Flight controller 101 e calculates the goal distance between the soundsource and the position at which the quality of the target sound reachesthe goal quality, using the distance between the current position ofunmanned aircraft 100 and the sound source, the quality of the targetsound from the sound source, and the relationship between apredetermined sound pressure level and the distance from the soundsource. Then, flight controller 101 e controls the movement of unmannedaircraft 100 so that unmanned aircraft 100 is located at the goaldistance measured from the sound source. Thus, when flying in thedirection away from the sound source, unmanned aircraft 100 flies to theposition at which the quality of the target sound reaches the goalquality and stays at this position not to move farther from the soundsource, for example.

If quality determiner 101 b determines that the quality of the targetsound is higher than the goal quality, flight controller 101 e controlsthe movement of unmanned aircraft 100 for flight-state control in thesound recording control so that unmanned aircraft 100 approaches thesound source, for example. As a result, unmanned aircraft 100 flies in adirection to approach the sound source.

When controlling the movement of unmanned aircraft 100 so that unmannedaircraft 100 approaches the sound source, flight controller 101 eperforms control so that unmanned aircraft 100 does not approach anycloser to the sound source than a position at a predetermined distancefrom the sound source, in accordance with: distance informationinstructing unmanned aircraft 100 not to approach any closer to thesound source than the position at the predetermined distance from thesound source; and the positional relationship obtained by sound sourcedeterminer 101 c. Thus, when flying in the direction to approach thesound source, unmanned aircraft 100 flies, to approach the sound source,to the position at the predetermined distance from the sound source anddoes not approach any closer to the sound source than this position, forexample.

Note that the distance information may be previously stored in a memoryor storage that is not shown, or in an external device. To be morespecific, flight controller 101 e may obtain the distance information byreading from the memory or storage that is not shown, or from theexternal device via communication IF 109.

Flight controller 101 e may perform the sound recording control whenfour microphones 105 pick up the target sound. When four microphones 105starts the target sound pickup, flight controller 101 e may stop thenormal control to start the sound recording control. Then, after the endof the target sound pickup, flight controller 102 e may stop the soundrecording control to start the normal control.

The sound recording control may be performed when four microphones 105pick up the target sound. More specifically, the sound recording controlmay be performed when only the target sound pickup is performed or whenthe image capture by camera 107 and the target sound pickup are bothperformed.

Video controller 101 f controls gimbal 106 according to the operationsignal received by communication IF 109. By doing so, video controller101 f controls the attitude of camera 107 so that the imaging directionof camera 107 is oriented in a direction indicated by the operationsignal. Moreover, video controller 101 f may perform predetermined imageprocessing on image data captured by camera 107. Video controller 101 fmay transmit the image data obtained from camera 107 or image dataobtained as a result of the predetermined image processing to mobileterminal 300 via communication IF 109.

Obstruction detector 101 g detects an obstruction around unmannedaircraft 100 according to the distance from unmanned aircraft 100 to asubject that is detected by ranging sensor 108. Obstruction detector 101g may detect an obstruction present in a direction in which unmannedaircraft 100 proceeds, by exchanging information with flight controller101 e. If detecting an obstruction present in the direction in whichunmanned aircraft 100 proceeds, obstruction detector 101 g may instructflight controller 101 e to move unmanned aircraft 100 to avoid theobstruction.

[2. Operation]

Next, an operation performed by unmanned aircraft 100 according to theembodiment is described.

FIG. 5 is a flowchart illustrating an example of an operation performedfor sound recording control of the unmanned aircraft according to theembodiment. FIG. 6 is a flowchart illustrating an example of a processperformed by the unmanned aircraft to determine quality of a targetsound. FIG. 7 illustrates an example of a method of calculating an S/Nratio as an indicator of the quality of the target sound.

As illustrated in FIG. 5, when sound-pickup processor 101 a starts thesound recording control, quality determiner 101 b of unmanned aircraft100 determines quality of the target sounds included in the four piecesof sound data generated by four microphones 105 (S11). For example, whenthe operation signal received from controller 200 includes a signalindicating a start of sound recording, sound pickup processor 101 astarts sound recording. The process performed in step S11 to determinethe quality of the target sound is described in detail, with referenceto FIG. 6 and FIG. 7.

As illustrated in FIG. 6, noise level calculator 101 ab of sound pickupprocessor 101 a calculates a sound pressure level of unprocessed soundsignal (including noise) for each of the four pieces of sound datagenerated by four microphones 105 (S21). For example, noise levelcalculator 101 ab obtains a signal before noise processing asillustrated in FIG. 7, as the sound data from microphone 105. The signalbefore noise processing is represented by a temporal change of anormalized number, for example. Thus, noise level calculator 101 abcalculates a temporal change of the sound pressure level by multiplyingamplitude of the signal before noise processing by a sound-pressureconversion factor corresponding to performance of correspondingmicrophone 105. Noise level calculator 101 ab extracts a predeterminedfrequency band from the calculated temporal change of the soundpressure. Then, noise level calculator 101 ab calculates the soundpressure level of the noise by calculating an average sound pressurelevel in a predetermined time duration (such as one second) from thetemporal change of the sound pressure level in the extractedpredetermined frequency band. Note that the predetermined frequency bandis predetermined to extract the target sound.

Noise level calculator 101 ab calculates the sound pressure level of thenoise using the signal before noise processing that is obtained frommicrophone 105. However, this is not intended to be limiting. Noiselevel calculator 101 ab may obtain, from a storage, a sound pressurelevel calculated using a signal obtained by previously picking up noisewhen no target sound is produced. In this case, the sound pressure levelcalculated using the previously-obtained signal is calculated using asignal obtained through sound recording performed corresponding to thenumber of revolutions of generator 110 of unmanned aircraft 100 for eachdifferent stage. This sound pressure level is associated with thecorresponding number of revolutions. More specifically, noise levelcalculator 101 ab may obtain the sound pressure level of the noise byreading, from the storage, the sound pressure level associated with thenumber of revolutions of generator 110 of unmanned aircraft 100.

Next, noise processor 101 aa of sound pickup processor 101 a performs,as the noise processing, the sound source separation process to separatethe obtained sound data into the target sound and the noise, which isrelated to flight of unmanned aircraft 100 (S22). As a result, a signalafter noise processing is obtained as illustrated in FIG. 7.

Next, noise level calculator 101 ab calculates a sound pressure level ofthe separated target sound (S23). As with the signal before noiseprocessing, the signal after noise processing is represented by atemporal change of a normalized number, for example. Thus, noise levelcalculator 101 ab calculates a temporal change of the sound pressurelevel by multiplying amplitude of the signal after noise processing by asound-pressure conversion factor corresponding to performance ofcorresponding microphone 105. Noise level calculator 101 ab extracts apredetermined frequency band from the calculated temporal change of thesound pressure. Then, noise level calculator 101 ab calculates the soundpressure level of the noise by calculating an average sound pressurelevel in a predetermined time duration (such as one second) from thetemporal change of the sound pressure level in the extractedpredetermined frequency band. Moreover, noise level calculator 101 abmay calculate the predetermined time duration used for calculating theaverage sound pressure level, using characteristics of the detectedtarget sound. More specifically, the predetermined time duration may beadjusted according to the characteristics of the detected target sound.Here, examples of such characteristics include a frequency band of thedetected target sound and a time length of the detected target sound.For example, noise level calculator 101 ab may increase thepredetermined time duration by determining whether the frequency band ofthe detected target sound is within a predetermined frequency band.Alternatively, noise level calculator 101 ab may decrease thepredetermined time duration with decrease in the time length of thedetected target sound.

Quality determiner 101 b calculates the S/N ratio of the target sound tothe noise, by subtracting the sound pressure level of the noise from thesound pressure level of the target sound using the sound pressure levelof the noise and the sound pressure level of the target sound calculatedby noise level calculator 101 ab (S24).

Next, quality determiner 101 b determines whether the calculated S/Nratio is the goal S/N ratio (S12). To be more specific, qualitydeterminer 101 b determines whether the calculated S/N ratio is within arange of S/N ratio with respect to the reference S/N ratio. Hereinafter,a range could be defined as +−5 dB, for example.

If quality determiner 101 b determines that the calculated S/N ratio isnot the goal S/N ratio (No in S12), the process proceeds to step S13. Incontrast, if quality determiner 101 b determines that the calculated S/Nratio is the goal S/N ratio (Yes in S12), the process proceeds to stepS17. If the S/N ratio is the goal S/N ratio, this means that unmannedaircraft 100 collects the target sound favorably. Thus, unmannedaircraft 100 is not moved.

Next, obstruction detector 101 g determines whether unmanned aircraft100 is safely movable (S13). More specifically, obstruction detector 101g determines whether a subject is present near unmanned aircraft 100. Ifdetermining that no subject is present near unmanned aircraft 100,obstruction detector 101 g determines that unmanned aircraft 100 issafely movable. If determining that a subject is present near unmannedaircraft 100, obstruction detector 101 g determines that unmannedaircraft 100 is not safely movable.

If obstruction detector 101 g determines that unmanned aircraft 100 issafely movable (Yes in S13), the process proceeds to Step S14. Incontrast, if obstruction detector 101 g determines that unmannedaircraft 100 is not safely movable (No in S13), the process proceeds tostep S17.

Quality determiner 101 b determines whether the calculated S/N ratio ishigher or lower than the goal S/N ratio (S14). In the present example,quality determiner 101 b determines whether the calculated S/N ratio ishigher or lower than the goal S/N ratio, using the range of plus orminus 1 with respect to the reference S/N ratio (−10 dB, for example).To be more specific, quality determiner 101 b determines whether thecalculated S/N ratio is higher than an upper limit (−9 dB, for example)of the range of the goal S/N ratio or lower than a lower limit (−11 dB,for example) of the range of the goal S/N ratio.

If quality determiner 101 b determines that the calculated S/N ratio ishigher than the range of the goal S/N ratio (“Higher” in S14), flightcontroller 101 e performs control to move unmanned aircraft 100 in thedirection away from the sound source (S15).

If quality determiner 101 b determines that the calculated S/N ratio islower than the range of the goal S/N ratio (“Lower” in S14), flightcontroller 101 e performs control to move unmanned aircraft 100 in thedirection to approach the sound source (S16).

Sound pickup processor 101 a determines whether to stop sound recording(S17). If sound pickup processor 101 a determines to stop soundrecording (Yes in S17), the sound recording control is ended. If soundpickup processor 101 a determines not to stop sound recording (No inS17), quality determiner 101 b makes the determination in step S11again.

FIG. 8A illustrates a first situation as an example of the operation forsound recording control of the unmanned aircraft according to theembodiment. FIG. 8B illustrates a second situation as an example of theoperation performed for sound recording control of the unmanned aircraftaccording to the embodiment. FIG. 8C illustrates a third situation as anexample of the operation performed for sound recording control of theunmanned aircraft according to the embodiment. FIG. 9A illustrates afourth situation as an example of the operation performed for soundrecording control of the unmanned aircraft according to the embodiment.FIG. 9B illustrates a fifth situation as an example of the operationperformed for sound recording control of the unmanned aircraft accordingto the embodiment. FIG. 9C illustrates a sixth situation as an exampleof the operation performed for sound recording control of the unmannedaircraft according to the embodiment. FIG. 10A illustrates a seventhsituation as an example of the operation performed for sound recordingcontrol of the unmanned aircraft according to the embodiment. FIG. 10Billustrates an eighth situation as an example of the operation performedfor sound recording control of the unmanned aircraft according to theembodiment. FIG. 10C illustrates a ninth situation as an example of theoperation performed for sound recording control of the unmanned aircraftaccording to the embodiment.

FIG. 8A to FIG. 8C, FIG. 9A to FIG. 9C, and FIG. 10A to FIG. 10Cillustrate operations performed by unmanned aircraft 100 viewed fromabove. FIG. 8A to FIG. 8C, FIG. 9A to FIG. 9C, and FIG. 10A to FIG. 10Cillustrate examples of the operation performed by unmanned aircraft 100to pick up a target sound when sound source 400 is a person by whom thetarget sound is emitted. In the examples illustrated in FIG. 8A to FIG.8C, FIG. 9A to FIG. 9C, and FIG. 10A to FIG. 10C, the reference S/Nratio is described as the goal S/N ratio. Broken line L illustrated inthe examples in FIG. 8A to FIG. 8C, FIG. 9A to FIG. 9C, and FIG. 10A toFIG. 10C is an imaginary line indicating a position at predetermineddistance d1 from sound source 400 that is indicated by the distanceinformation. More specifically, broken line L1 indicates a boundary of asafety area to ensure the safety of the sound source.

In a situation illustrated in FIG. 8A, the sound pressure level of thenoise is calculated at 75 dB and the sound pressure level of the targetsound is calculated at 70 dB, from which the S/N ratio is calculated at−5 dB. Here, the goal S/N ratio is set at −10 dB, and the calculated S/Nratio is higher than the goal S/N ratio. Thus, unmanned aircraft 100moves in the direction away from sound source 400 as illustrated in FIG.8B. In a situation illustrated in FIG. 8B, unmanned aircraft 100 usesthe sound data obtained from microphone 105 after moving away from soundsource 400. As a result, the sound pressure level of the noise iscalculated at 75 dB and the sound pressure level of the target sound iscalculated at 70 dB, from which the S/N ratio is calculated at −10 dB asillustrated in FIG. 8B. In this case, the calculated S/N ratio is withinthe range of the goal S/N ratio. Thus, unmanned aircraft 100 does notmove, and thus maintains a distance from sound source 400 as illustratedin FIG. 8C.

In a situation illustrated in FIG. 9A, the sound pressure level of thenoise is calculated at 75 dB and the sound pressure level of the targetsound is calculated at 65 dB, from which the S/N ratio is calculated at−10 dB. Here, the goal S/N ratio is set at −10 dB, and the calculatedS/N ratio is within the range of the goal S/N ratio. Thus, unmannedaircraft 100 does not move, and thus maintains a distance from soundsource 400 as illustrated in FIG. 9A. Next, FIG. 9B illustrates asituation in which sound source 400 approaches unmanned aircraft 100. Inthis case, unmanned aircraft 100 uses the sound data obtained frommicrophone 105 after sound source 400 approaches unmanned aircraft 100.As a result, the sound pressure level of the noise is calculated at 75dB and the sound pressure level of the target sound is calculated at 69dB, from which the S/N ratio is calculated at −6 dB. The calculated S/Nratio is higher than the goal S/N ratio. Thus, unmanned aircraft 100moves in the direction away from sound source 400 as illustrated in FIG.9C. In a situation illustrated in FIG. 9C, unmanned aircraft 100 usesthe sound data obtained from microphone 105 after moving away from soundsource 400. As a result, the sound pressure level of the noise iscalculated at 75 dB and the sound pressure level of the target sound iscalculated at 65 dB, from which the S/N ratio is calculated at −10 dB.In this case, the calculated S/N ratio is within the range of the goalS/N ratio. Thus, unmanned aircraft 100 does not move, and thus maintainsa distance from sound source 400 as illustrated in FIG. 9C.

In a situation illustrated in FIG. 10A, the sound pressure level of thenoise is calculated at 75 dB and the sound pressure level of the targetsound is calculated at 58 dB, from which the S/N ratio is calculated at−17 dB. Here, the goal S/N ratio is set at −10 dB, and the calculatedS/N ratio is lower than the goal S/N ratio. Thus, unmanned aircraft 100moves in the direction to approach sound source 400 as illustrated inFIG. 10B. In a situation illustrated in FIG. 10B, unmanned aircraft 100uses the sound data obtained after approaching sound source 400. As aresult, the sound pressure level of the noise is calculated at 75 dB andthe sound pressure level of the target sound is calculated at 61 dB,from which the S/N ratio is calculated at −14 dB. In this case, thecalculated S/N ratio is still lower than the goal S/N ratio. Thus,unmanned aircraft 100 moves in the direction to further approach soundsource 400 as illustrated in FIG. 10C. In a situation illustrated inFIG. 10C, unmanned aircraft 100 uses the sound data obtained afterfurther approaching sound source 400. As a result, the sound pressurelevel of the noise is calculated at 75 dB and the sound pressure levelof the target sound is calculated at 63 dB, from which the S/N ratio iscalculated at −12 dB. In this case, the calculated S/N ratio is stilllower than the goal S/N ratio. However, unmanned aircraft 100 is atpredetermined distance d1 from sound source 400. Thus, unmanned aircraft100 does not move any more in the direction to approach the soundsource.

Although the positional relationship between unmanned aircraft 100 andsound source 400 is described above using the distance in a horizontaldirection, a distance in a three-dimensional space may be used. In thiscase, the safety area, which is defined by predetermined distance d1indicated by the distance information used for controlling unmannedaircraft 100 moving in the direction to approach sound source 400, maybe defined by the distance in the three-dimensional space instead of thedistance in the horizontal direction as described above as an example.

FIG. 11A illustrates a tenth situation as an example of the operationfor sound recording control of the unmanned aircraft according to theembodiment. FIG. 11B illustrates an eleventh situation as an example ofthe operation performed for sound recording control of the unmannedaircraft according to the embodiment. FIG. 12A illustrates a twelfthsituation as an example of the operation performed for sound recordingcontrol of the unmanned aircraft according to the embodiment. FIG. 12Billustrates a thirteenth situation as an example of the operationperformed for sound recording control of the unmanned aircraft accordingto the embodiment. Note that each of FIG. 11A, FIG. 11B, FIG. 12A, andFIG. 12B is an example illustrating the safety area and the positionalrelationship between the unmanned aircraft and the sound source viewedin the horizontal direction.

In a situation illustrated in FIG. 11A, the sound pressure level of thenoise is calculated at 75 dB and the sound pressure level of the targetsound is calculated at 68 dB, from which the S/N ratio is calculated at−7 dB. Here, the goal S/N ratio is set at −10 dB, and the calculated S/Nratio is higher than the goal S/N ratio. Thus, flight controller 101 eperforms control to move unmanned aircraft 100 in the direction awayfrom sound source 400. When performing control to move unmanned aircraft100 in the direction away from the sound source in this way, flightcontroller 101 e may perform control to move unmanned aircraft 100 inthe horizontal direction without control to cause unmanned aircraft 100to ascend as illustrated in FIG. 11B. In this case, flight controller101 e may perform control to move unmanned aircraft 100 in a directionto further approach the ground.

As a result, when moving away from the sound source, unmanned aircraft100 moves in the horizontal direction away from the sound source insteadof ascending to move away from the sound source. Thus, unmanned aircraft100 maintains a distance from the sound source in the horizontaldirection. In this case, unmanned aircraft 100 does not move higher thanthe current position. Thus, an impact in case of falling of unmannedaircraft 100 can be reduced to ensure the safety of the sound source. Inthe above description, unmanned aircraft 100 moves in the direction awayfrom the sound source as an example. However, even when unmannedaircraft 100 moves in the direction to approach the sound source, thesame effect can be achieved.

In a situation illustrated in FIG. 12A, the sound pressure level of thenoise is calculated at 75 dB and the sound pressure level of the targetsound is calculated at 59 dB, from which the S/N ratio is calculated at−16 dB. Here, the goal S/N ratio is set at −10 dB, and the calculatedS/N ratio is lower than the goal S/N ratio. Thus, flight controller 101e performs control to move unmanned aircraft 100 in the direction toapproach sound source 400. When performing control to move unmannedaircraft 100 in the direction to approach the sound source in this way,flight controller 101 e may perform control so that unmanned aircraft100 approaches the ground as illustrated in FIG. 12B.

As a result, when approaching the sound source, unmanned aircraft 100moves in the direction to approach the ground to approach the soundsource instead of moving in the horizontal direction to approach thesound source. This allows unmanned aircraft 100 to approach the soundsource while maintaining the distance from the sound source in thehorizontal direction. In this way, unmanned aircraft 100 is closer tothe ground than the current position is. Thus, an impact in case offalling of unmanned aircraft 100 can be reduced to ensure the safety ofthe sound source. In the above description, unmanned aircraft 100 movesin the direction to approach the sound source as an example. However,even when unmanned aircraft 100 moves in the direction away from thesound source, the same effect can be achieved.

[3. Advantageous Effects Etc.]

Processor 101 of unmanned aircraft 100 according to the presentembodiment determines quality of a target sound using sound datagenerated by microphone 105. Processor 101 obtains a positionalrelationship between unmanned aircraft 100 and sound source 400 of thetarget sound using data generated by the sensor. Processor 101 controlsmovement of unmanned aircraft 100 to control a distance between unmannedaircraft 100 and sound source 400 of the target sound, in accordancewith the quality of the target sound and the positional relationship.Thus, the quality of the target sound can be ensured while the distancebetween unmanned aircraft 100 and sound source 400 is controlled. Thisenables sound recording of appropriate sound quality in addition toensuring safety of sound source 400.

When the quality of the target sound is higher than a predetermined goalquality, processor 101 of unmanned aircraft 100 controls the movement ofunmanned aircraft 100 so that unmanned aircraft 100 moves away fromsound source 400. In this way, unmanned aircraft 100 moves in thedirection to away from sound source 400 when the quality of the targetsound is ensured. This further enhances the safety of sound source 400.

When controlling the movement of unmanned aircraft 100 so that unmannedaircraft 100 moves away from sound source 400, processor 101 of unmannedaircraft 100 controls the movement of unmanned aircraft 100 so thatunmanned aircraft 100 moves to any position between a current positionof unmanned aircraft 100 and a position at which the quality of thetarget sound reaches the predetermined goal quality. Thus, unmannedaircraft 100 moves away from sound source 400 within an area to ensurethe quality of the target sound.

When the quality of the target sound is lower than the predeterminedgoal quality, processor 101 of unmanned aircraft 100 controls themovement of unmanned aircraft 100 so that unmanned aircraft 100approaches the sound source. In this way, unmanned aircraft 100 moves inthe direction to approach sound source 400 when the quality of thetarget sound is not ensured. This enhances the quality of the targetsound.

Processor 101 of unmanned aircraft 100 calculates a signal-to-noise(S/N) ratio using the target sound and noise related to flight ofunmanned aircraft 100, as an indicator for determining the quality.Moreover, processor 101 further obtains, as the predetermined goalquality, a goal S/N ratio precalculated using the S/N ratio calculatedusing the target sound and the noise related to the flight of unmannedaircraft 100. Then, processor 101 determines the quality of the targetsound by comparing the goal S/N ratio obtained and the S/N ratiocalculated. This allows the quality of the target sound to be easilydetermined.

The sensor of unmanned aircraft 100 includes an image sensor that isincluded in camera 107 and that generates image data. Processor 101obtains the positional relationship using the image data generated bythe image sensor. In this way, processor 101 obtains the positionalrelationship additionally using the image data. Thus, the positionalrelationship with high precision can be obtained.

The sensor of unmanned aircraft 100 further includes ranging sensor 108that generates ranging data. Processor 101 obtains the positionalrelationship using the ranging data generated by ranging sensor 108. Inthis way, the processor obtains the positional relationship additionallyusing the ranging data. Thus, the positional relationship with highprecision can be obtained.

Processor 101 of unmanned aircraft 100 determines a goal distance inaccordance with the quality of the target sound, the positionalrelationship, and the predetermined goal quality. Then, processor 101controls the movement of unmanned aircraft 100 so that the distancebetween unmanned aircraft 100 and sound source 400 reaches the goaldistance. As a result, unmanned aircraft 100 can move to the positioncorresponding to the predetermined goal quality.

[4. Variations] [4-1. Variation 1]

For unmanned aircraft 100 according to the above embodiment, thereference S/N ratio for the goal S/N ratio used as the goal quality isdescribed as one value, such as −10 dB. However, this is not limited toone value. More than one value may be set according to purposes of soundrecording control.

FIG. 13 is a table illustrating an example of a relationship between thereference S/N ratio and the purpose. When the goal S/N ratio isrepresented by a threshold value instead of the goal range of plus orminus 1 dB, the reference S/N ratio may be understood as the goal S/Nratio.

As illustrated in FIG. 13, the reference S/N ratio may be set for eachof four stages corresponding to purposes. In this table, R1 to R4 have arelationship expressed as R1<R2<R3<R4. For example, the reference S/Nratio for the lowest quality is R1, and the reference S/N ratio fortypical sound collection is R2. The reference S/N ratio for relaybroadcast is R3, and the reference S/N ratio for broadcast of highquality is R4. One of these purposes is selected through an operationperformed on controller 200 by the user. Then, the reference S/N ratiocorresponding to the selected purpose is used for the sound recordingcontrol of unmanned aircraft 100. The purpose may be fixed according toan application used by controller 200. In this case, the reference S/Nratio corresponding to the application is used for the sound recordingcontrol of unmanned aircraft 100.

[4-2. Variation 2]

Flight controller 101 e of unmanned aircraft 100 according to the aboveembodiment performs control to move unmanned aircraft 100 in thedirection away from the sound source if quality determiner 101 bdetermines that the calculated S/N ratio is higher than the range of thegoal S/N ratio. However, unmanned aircraft 100 may be controlled not tomove in this case. This is because sound recording in this case isperformed with sufficiently high quality.

[4-3. Variation 3]

When reaching the position at predetermined distance d1 from the soundsource, unmanned aircraft 100 according to the above embodiment iscontrolled not to move even if the calculated S/N ratio is lower thanthe goal S/N ratio. However, further control may be performed in thiscase. To be more specific, if the quality of the target sound is lowerthan the predetermined goal quality after unmanned aircraft 100 iscontrolled to move, to approach the sound source, to the position at thepredetermined distance from the sound source in accordance with thedistance information and the positional relationship, unmanned aircraft100 is controlled not to move. However, this is not intended to belimiting.

For example, if an actuator, which is not shown, is included in unmannedaircraft 100 to change an orientation of microphone 105, processor 101may control the actuator to change the orientation of microphone 105.More specifically, a direction in which microphone 105 has a highsensitivity may be oriented toward the sound source. This aligns thehigh-sensitivity direction of microphone 105 with the direction of thesound source. Thus, the sound pressure level of the target sound withrespect to the sound pressure level of the noise can be relativelyincreased, which enhances the quality of sound recording.

Moreover, if unmanned aircraft 100 includes an actuator that changes anamount of outward projection of microphone 105 from unmanned aircraft100, the actuator may be controlled to change the amount of outwardprojection of microphone 105. More specifically, microphone 105 mayproject outwardly from unmanned aircraft 100 to approach the soundsource. As a result, microphone 105 is distanced from unmanned aircraft100 that is a noise source, and thus the sound pressure level of thenoise can be reduced. Moreover, microphone 105 approaches the soundsource in this case. Thus, the sound pressure level of the target soundwith respect to the sound pressure level of the noise can be relativelyincreased. This effectively enhances the quality of sound recording.Note that the actuator may include the actuator that changes theorientation of microphone 105 and the actuator that changes the amountof projection of microphone 105. Then, processor 101 may control both ofthese actuators to change the orientation and the amount of projectionof microphone 105. Note that the direction of projecting outwardly fromunmanned aircraft 100 refers to a horizontal lateral direction ofunmanned aircraft 100. Furthermore, if the quality of the target soundis lower than the goal quality after unmanned aircraft 100 is controlledto approach the sound source, control may be performed so that at leastone of the orientation of microphone 105 or the amount of outwardprojection of microphone 105 from unmanned aircraft 100 may be changed.

[4-4. Variation 4]

Unmanned aircraft 100 according to the above embodiment includes fourgenerators 100. However, the number of generators included in unmannedaircraft 100 is not limited to four. The number of generators may be oneto three, or at least five.

[4-5. Variation 5]

Unmanned aircraft 100 according to the above embodiment includes mainbody 140 that is connected to four ducts 130 via four arms 141. However,this is not intended to be limiting. Four ducts 130 or four arms 141 maynot be included if four generators 110 are connected to main body 140.To be more specific, the unmanned aircraft may include four generators110 directly connected to main body 140 or include four ducts 130directly connected main body 140. Alternatively, the unmanned aircraftmay not include four ducts 130, or more specifically, may include fourgenerators 110 that are not covered laterally.

[4-6. Variation 6]

Unmanned aircraft 100 according to the above embodiment includes fourmicrophones 105. However, the number of microphones included in unmannedaircraft 100 is not limited to four and may be one to three, or at leastfive. If the number of microphones 105 is small, a plurality of piecesof sound data may be obtained at different timings by rotating theattitude of unmanned aircraft 100. Then, the sound source direction maybe estimated by comparing the plurality of pieces of sound data.Microphone 105 may be disposed outside unmanned aircraft 100, or morespecifically, exposed to the outside. Microphone 105 may be disposedlateral to arm 141 instead of being lateral to main body 140. Moreover,microphone 105 may be disposed at a distance from main body 140. Forexample, microphone 105 may be disposed at an end or some point of anarm-like rod, a line like a metallic wire, or a string-like cord that isattached to main boy 140 separately from arm 141 and extends in adirection away from main body 140.

[4-7. Variation 7]

The above embodiment describes an example in which the orientation ofmicrophone 105 is changed if the S/N ratio is still lower than the goalS/N ratio even after the distance to sound source 400 reachespredetermined distance d1. However, this is not intended to be limiting.The high-sensitivity direction of microphone 105 may be previouslyaligned with the sound source direction, and then the operationdescribed with reference to FIG. 5 in the above embodiment may beperformed. For unmanned aircraft 100 including an actuator that changesthe orientation of microphone 105, the actuator may be controlled tochange the orientation of microphone 105 to align the high-sensitivitydirection of microphone 105 with the sound source direction. Forunmanned aircraft 100 including no actuator, the flight attitude ofunmanned aircraft 100 may be controlled to align the high-sensitivitydirection of microphone 105 with the sound source direction.

Note that, if the flight attitude of unmanned aircraft 100 is controlledto align the high-sensitivity direction of microphone 105 with the soundsource direction, information indicating a range that includes ahigh-sensitivity direction with respect to unmanned aircraft 100 ispreviously stored for each of four microphones 105 in a memory that isnot shown but included in unmanned aircraft 100. Thus, qualitydeterminer 101 b can determine an amount of change made by flightcontroller 101 e in the attitude of unmanned aircraft 100, in accordancewith the information on the high-sensitivity direction read from thememory and the attitude of unmanned aircraft 100 obtained from thesensors, such as acceleration sensor 103 and gyroscope sensor 104. Thisamount of change indicates the amount of rotation of unmanned aircraft100 to align the sound source direction with the high-sensitivitydirection.

[4-8. Variation 8]

Unmanned aircraft 100 according to the above embodiment starts soundrecording if the operation signal received from controller 200 includesthe signal indicating the start of sound recording. However, this is notintended to be limiting. For example, sound recording may be started ifthe sound data obtained by sound pickup processor 101 a includes a soundrecording command indicating the start of sound recording.Alternatively, sound recording may be started if a gesture of the userindicating the start of sound recording is recognized through analysisof image data obtained by camera 107 or if a speech indicating the startof sound recording is recognized from lip movements of the user.Moreover, recognition of the gesture or speech of specific key wordsmade by the user may be used for adjusting predetermined distance d1.

Unmanned aircraft 100 may fly autonomously according to a predeterminedset program, instead of being controlled by controller 200.

Controller 200 may control unmanned aircraft 100 according to apredetermined set program without an operation interface of unmannedaircraft 100.

[4-9. Variation 9]

Although unmanned aircraft 100 according to the above embodiment usesthe S/N ratio as an evaluation indicator of the quality of soundrecording, this is not intended to be limiting. A confidence coefficientobtained after audio recognition processing or an error rate of audiorecognition may be used as the evaluation indicator of the quality.

[4-10. Variation 10]

Unmanned aircraft 100 according to the above embodiment may control themovement using information on a frequency of the target sound and afrequency of the flight sound (that is, noise) of unmanned aircraft 100.To be more specific, quality determiner 101 b determines a difference infrequency between the target sound and the flight sound. In accordancewith this difference, flight controller 101 e controls whether unmannedaircraft 100 is to approach or move away from the sound source.Processing according to the present variation is described withreference to FIG. 14. FIG. 14 is a flowchart illustrating an example ofthe operation for sound recording control of the unmanned aircraftaccording to Variation 10.

Quality determiner 101 b determines the frequency of the target soundand the frequency of the flight sound (S31). In step S31, a frequencyband of the target sound and a frequency band of the flight sound may bedetermined.

Next, quality determiner 101 b determines whether a difference infrequency between the target sound and the flight sound is smaller thanor equal to a threshold value (S32). If frequency bands are determinedin step S31, a difference between center frequencies of the respectivefrequency bands may be used as the difference in frequency.

If the difference in frequency between the target sound and the flightsound is determined as exceeding the threshold value (No in S32), flightcontroller 101 e performs flight control to move unmanned aircraft 100away from the sound source (S33). When the difference in frequency issufficiently large in this way, the quality of sound recording after theflight sound, that is, the noise, is filtered out from the picked soundcan be adequately maintained even if unmanned aircraft 100 moves awayfrom the target.

In contrast, if the difference in frequency between the target sound andthe flight sound is determined as being smaller than or equal to thethreshold value (Yes in S32), flight controller 101 e performs flightcontrol so that unmanned aircraft 100 approaches the sound source (S34).Such a small difference in frequency results in difficulty inmaintaining the quality of sound recording after the flight sound, thatis, the noise, is filtered out from the picked sound. For this reason,unmanned aircraft 100 is caused to approach the sound source.

After flight control of step S33 or S34 is performed, sound pickupprocessor 101 a determines whether to stop sound recording (S35). Ifdetermining to stop sound recording (Yes in S35), sound pickup processor101 a ends sound control. If determining not to stop sound recording (Noin S35), sound pickup processor 101 a makes determination in step S31again.

Such control of the distance from the sound source in accordance withthe difference in frequency between the target sound and the flightsound (that is, the noise) eventually enables control of the distancebetween the sound source and unmanned aircraft 100 according to thequality of sound recording (the S/N ratio, for example).

[4-11. Variation 11]

Unmanned aircraft 100 according to the above embodiment may control theflight sound to suppress flight control. To be more specific, flightcontroller 101 e controls propeller revolution in accordance with adifference in frequency between the target sound and the flight sound.Processing according to the present variation is described withreference to FIG. 15. FIG. 15 is a flowchart illustrating an example ofthe operation for sound recording control of the unmanned aircraftaccording to the present variation. Description on processes that aresubstantially the same as those in FIG. 14 is not repeated here.

Quality determiner 101 b determines the frequency of the target soundand the frequency of the flight sound (S31).

Next, quality determiner 101 b determines whether a difference infrequency between the target sound and the flight sound is smaller thanor equal to a threshold value (S32).

If the difference in frequency between the target sound and the flightsound is determined as exceeding the threshold value (No in S32), flightcontroller 101 e performs flight control to move unmanned aircraft 100away from the sound source (S33).

In contrast, if the difference in frequency between the target sound andthe flight sound is determined as being smaller than or equal to thethreshold value (Yes in S32), flight controller 101 e controls thepropeller revolution to increase the difference in frequency (S36). Forexample, flight controller 101 e changes the number of propellerrevolutions so that the difference in frequency between the flight soundand the target sound increases.

Such flight control performed to increase the difference in frequencybetween the target sound and the flight sound enhances the quality ofsound recording. Moreover, such control keeps unmanned aircraft 100 fromapproaching the sound source.

Note that after the movement control or flight control is performed inaccordance with the difference in frequency between the target sound andthe flight sound according to Variation 11 or 12, the movement controlbased on the quality of sound recording may be performed as in the aboveembodiment.

[4-12. Variation 12]

Unmanned aircraft 100 according to the above embodiment may move withinan area in which the quality of the target sound satisfies the goalquality. To be more specific, flight controller 101 e determines, as amovement allowance area, the area in which the quality of the targetsound satisfies the goal quality, and then limits the movement ofunmanned aircraft 100 within this movement allowance area. For example,when receiving the operation signal from controller 200, flightcontroller 101 e performs an operation to move unmanned aircraft 100within the movement allowance area and does not perform an operation tomove unmanned aircraft 100 outside the movement allowance area.

Each of the components in the above embodiment may be configured withdedicated hardware or may be implemented by executing a software programsuitable for the component. Each of the components may be implemented bya program executer, such as a CPU or a processor, reading and executinga software program recorded on a hard disk or a non-temporary recordingmedium, such as a semiconductor memory. Here, software that implements,for example, unmanned aircraft 100 and the information processing methodaccording to the above embodiment is the following program.

More specifically, this program is an information processing methodexecuted by a processor, which is a computer, included in an unmannedaircraft that includes the processor and a sensor including at least amicrophone that generates sound data. The information processing methodincludes: determining quality of a target sound using the sound datagenerated by the microphone; obtaining a positional relationship betweenthe unmanned aircraft and a sound source of the target sound using datagenerated by the sensor; and controlling movement of the unmannedaircraft to control a distance between the unmanned aircraft and thesound source of the target sound, in accordance with the quality of thetarget sound and the positional relationship.

Although the unmanned aircraft, the information processing method, andthe program in an aspect or aspects according to the present disclosurehave been described by way of the above embodiment, it should be obviousthat the present disclosure is not limited to the above embodiment.Other embodiments implemented through various changes and modificationsconceived by a person of ordinary skill in the art or through acombination of the structural elements in different embodimentsdescribed above may be included in the scope in an aspect or aspectsaccording to the present disclosure, unless such changes, modifications,and combination depart from the scope of the present disclosure.

Note that machine learning may be used in: the processes performed byquality determiner 101 b, sound source determiner 101 c, obstructiondetector 101 g, and flight controller 101 e; the image recognitionprocessing; and the sound recognition processing. Types of machinelearning algorithms include, for example: supervised learning algorithmsthat learn a relationship between an input and an output using trainingdata given a label (output information) associated with inputinformation; unsupervised learning algorithms that find a data structurefrom only unlabeled inputs; semi-supervised learning that approachesboth labeled training data and unlabeled training data; andreinforcement learning algorithms that learn a set of actions leading tothe highest reward by receiving feedback (reward) from an action chosenas a result of state observation. Specific approaches of machinelearning include: a neural network (including deep learning using amulti-layered neural network); genetic programming; decision tree;Bayesian network; and support vector machine (SVM). Any one of theaforementioned specific examples may be used in the present disclosure.

Although only the exemplary embodiment of the present disclosure hasbeen described in detail above, those skilled in the art will readilyappreciate that many modifications are possible in the exemplaryembodiment without materially departing from the novel teachings andadvantages of the present disclosure. Accordingly, all suchmodifications are intended to be included within the scope of thepresent disclosure.

INDUSTRIAL APPLICABILITY

The present disclosure is useful as an unmanned aircraft, an informationprocessing method, and a program that are capable of enhancing thequality of a target sound.

1. An unmanned aircraft, comprising: a sensor that includes at least amicrophone that generates sound data; and a processor, wherein theprocessor determines quality of a target sound using the sound datagenerated by the microphone, obtains a positional relationship betweenthe unmanned aircraft and a sound source of the target sound using datagenerated by the sensor, and controls movement of the unmanned aircraftto control a distance between the unmanned aircraft and the sound sourceof the target sound, in accordance with the quality of the target soundand the positional relationship.
 2. The unmanned aircraft according toclaim 1, wherein when the quality of the target sound is higher than apredetermined goal quality, the processor causes the unmanned aircraftto move away from the sound source.
 3. The unmanned aircraft accordingto claim 2, wherein when causing the unmanned aircraft to move away fromthe sound source, the processor causes the unmanned aircraft to move toany position between a current position of the unmanned aircraft and aposition at which the quality of the target sound reaches thepredetermined goal quality.
 4. The unmanned aircraft according to claim1, wherein when the quality of the target sound is lower than thepredetermined goal quality, the processor causes the unmanned aircraftto approach the sound source.
 5. The unmanned aircraft according toclaim 4, wherein the processor further obtains distance informationindicating a predetermined distance from the sound source, and whencausing the unmanned aircraft to approach the sound source, theprocessor controls the movement of the unmanned aircraft in accordancewith the distance information and the positional relationship to causethe unmanned aircraft not to approach any closer to the sound sourcethan a position at the predetermined distance from the sound source. 6.The unmanned aircraft according to claim 5, further comprising: anactuator that changes at least one of an orientation of the microphoneor an amount of outward projection of the microphone from the unmannedaircraft, wherein when the quality of the target sound is lower than thepredetermined goal quality even after the processor controls themovement of the unmanned aircraft in accordance with the distanceinformation and the positional relationship to cause the unmannedaircraft to move, to approach the sound source, to the position at thepredetermined distance from the sound source, the processor causes theactuator to change at least one of the orientation of the microphone orthe amount of outward projection of the microphone from the unmannedaircraft.
 7. The unmanned aircraft according to claim 1, wherein theprocessor calculates a signal-to-noise (S/N) ratio using the targetsound and noise related to flight of the unmanned aircraft, as anindicator for determining the quality.
 8. The unmanned aircraftaccording to claim 7, wherein the processor further obtains a goal S/Nratio precalculated using the noise related to the flight of theunmanned aircraft, as the predetermined goal quality, and determines thequality of the target sound by comparing the goal S/N ratio obtained andthe S/N ratio calculated.
 9. The unmanned aircraft according to claim 1,wherein the processor causes the unmanned aircraft to approach ground.10. The unmanned aircraft according to claim 1, wherein the sensorfurther includes an image sensor that generates image data, and theprocessor obtains the positional relationship using the image datagenerated by the image sensor.
 11. The unmanned aircraft according toclaim 1, wherein the sensor further includes a ranging sensor thatgenerates ranging data, and the processor obtains the positionalrelationship using the ranging data generated by the ranging sensor. 12.The unmanned aircraft according to claim 1, wherein the processordetermines a goal distance between the unmanned aircraft and the soundsource in accordance with the quality of the target sound, thepositional relationship, and the predetermined goal quality, andcontrols the movement of the unmanned aircraft to achieve the goaldistance.
 13. The unmanned aircraft according to claim 1, wherein thepositional relationship is at least one of (i) the distance between theunmanned aircraft and the sound source, (ii) a position of the soundsource with respect to the unmanned aircraft, or (iii) a direction fromthe unmanned aircraft to the sound source.
 14. An information processingmethod used by a processor included in an unmanned aircraft, theunmanned aircraft including the processor and a sensor, the sensorincluding at least a microphone that generates sound data, theinformation processing method comprising: determining quality of atarget sound using the sound data generated by the microphone; obtaininga positional relationship between the unmanned aircraft and a soundsource of the target sound using data generated by the sensor; andcontrolling movement of the unmanned aircraft to control a distancebetween the unmanned aircraft and the sound source of the target sound,in accordance with the quality of the target sound and the positionalrelationship.
 15. A non-transitory computer-readable recording mediumfor use in a processor included in an unmanned aircraft that includesthe processor and a sensor, the sensor including at least a microphonethat generates sound data, the recording medium having a computerprogram recorded thereon for causing the processor to execute aninformation processing method comprising: determining quality of atarget sound using the sound data generated by the microphone; obtaininga positional relationship between the unmanned aircraft and a soundsource of the target sound using data generated by the sensor; andcontrolling movement of the unmanned aircraft to control a distancebetween the unmanned aircraft and the sound source of the target sound,in accordance with the quality of the target sound and the positionalrelationship.